Lay Theme Forum

Hi all,
I can't seem to figure to style the Site Title - anyone who can guide me?
Text Formats is not the place (I think...) and I can't seem to find any other logic place. I want to have a different formating for desktop and phone usage - ie. for Phone, I'd like the title not cantered (default) but left-aligned and bold. - how can I control and differentiate this?
Thanks!!